高效氨吸附用载锌活性炭的结构表征及氨吸附动力学研究

The structural characterization and adsorption kinetics of ammonia for highly-efficient ammonia adsorption activated carbon loaded by zinc

采用不同浓度的ZnCl_2溶液对椰壳活性炭进行表面改性以制备高容量氨吸附用活性炭,并采用低温液氮吸附(BET)、扫描电镜(SEM)、Boehm滴定对改性前后活性炭的物理结构及表面含氧官能团进行了测定,同时以常温动态吸附对氨吸附容量及吸附动力学进行了研究,并对ZnCl_2活性炭氨吸附去除机理进行了分析。结果表明:改性后活性炭微孔数量减少,介孔比例提高;随ZnCl_2浓度的增加,活性炭的比表面积、孔容减小,平均孔径变大,介孔所占比例由23.00%增加到25.52%;改性后活性炭表面含氧官能团含量增加,质量比为11%的ZnCl_2浸渍的活性炭样品(AC3)总酸性含氧官能团增加最多,增加了0.259mmol·g^(-1)。浸渍ZnCl_2溶液改性对活性炭吸附氨性能的改善十分明显,样品AC3对氨气的吸附量(75.58 mg·g-1)为原始活性炭(12.5 mg·g-1)的6.05倍;吸附动力学模型研究得出,氨在改性前后活性炭样品上的吸附与准二阶动力学模型较符合,说明吸附反应过程为物理-化学联合吸附。

Activated carbon for ammonia removal was modified via ZnCl2 impregnation of coconut shell based activated carbon. Ni- trogen adsorption isotherm（BET）, scanning electron microscopy（SEM） and Boehm titration were used to characterize the surface struc- tures and surface oxygen containing functional groups of the activated carbon before and after modification. Dynamic ammonia adsorption at room temperature was used for adsorption performance test. The adsorption kinetics and adsorption removal mechanism of the activated carbons for ammonia were also studied. Results showed that after modification by ZnCl2, the surface area and pore volume of activated carbon decreased, together with average pore diameter increased as the concentration of the ZnCl2 increased, the ratio of mesopore increased from 23.00% to 25.52%. After modification, oxygen containing groups on the surface of activated carbon increased,the most one was the activated carbon modified with 11% ZnCl2 which increased 0.259 mmol·g^-1. The ZnC12 modification was conducive to the adsorption of activated carbon on ammonia. Ammonia adsorption capacity of the modified activated carbon （75.58 mg·g^-1） was 6.05 times higher that of the original one （12.5mg·g^-1）. The adsorption dynamics process of ammonia conforms to the quasi second order kinetics mode. The adsorption process of the ammonia on the activated carbon before and after modification was the physical and chemical adsorption.